A native ribonucleoprotein (RNP) complex of AMV was prepared under conditions that gave optimal cDNA synthesis. The complex was an autonomous transcriptional unit capable of synthesizing DNA in the absence of exogenous reverse transcriptase, genomic RNA and primer. The principle polypeptide constituent of the RNP complex is the highly basic protein P12 at a molar ratio of 40:1 in relation to the beta subunit of the polymerase. When examined by E.M. the RNP beta complex appears similar to the beaded structure of chromatin fiber. A significant portion of these molecules are circular with head-like structures. Utilizing a reconstituted system of Avian Myeloblastosis Virus genome and reverse transcriptase, we have synthesized both the negative and positive DNA strand of AMV RNA. The product of the two-step reaction is a linear duplex of 5.2 x 10 to the 6th power daltons is covalently linked and 95-100% S1 rsistant. Endogenous proviral sequences are randomly integrated in the chromatin of CEF. However, when CEF were transformed by RSV molecular hybridization revealed that most of the exogenous proviral sequences were integrated within the light chromatin fraction. AMV contains a DNA endonuclease that is preferentially specific for superhelical double-stranded DNA's of phage phi X174 and SV-40.